That's correct, but if the area of the inlet (or its hydraulic equivalent) is less than the outlet, then the coolant should "shoot" down, hitting the baseplate.
I ran some calculations earlier, and this "ratio" (inlet to outlet) actually varies greatly, from 0.2 to 1.5, for diameters ranging from 0 to 3/4. There's kind of a linear progression, but not completely. It was an old calculation though, based on inlet tube diameter, and exiting channel area.
In the simulation, there weren't any flow seperators, so the coolant hit the top of the fins, instead of the baseplate. The resulting disturbance causes the water to ignore the deadspot, at the corner. If you look at the first graph, you can see a red spot (high speed), righ on top of the fin. I believe that that hot spot actually acts as a flow restriction.
I was looking at this earlier, and if I use a nozzle that's 1/4 inch diameter, that would address exactly what you wrote about. The exiting channel area ratio is favorable (for the water to shoot down). Now I just have to calculate the resulting pressure drop, and recalculate the channel exit's hydraulic equivalent, and double check all my calculations...
Here's a pic of the 1/4 diameter:
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